Heretofore others have provided rock door and concave structures for agricultural harvesters wherein the rock door is disposed between the feeder conveyor and the threshing rotor. Two such prior constructions are illustrated in patents U.S. Pat. No. 3,124,138 to R. Claas for "Threshing Machine Having a Specific Cylinder and Concave" issued Mar. 10, 1964 and U.S. Pat. No. 3,089,299 issued to R. Claas on May 14, 1963 for a "Stone Trap For Combines".